Catelynn Lowell Must Be Loving Tyler Baltierra's Total Transformation (PHOTO)

The lanky, skinny Tyler Baltierra you've known and loved since meeting him on MTV's 16 and Pregnant way back when appears to have left the building. In his place: A buff, grown-up guy with semi-washboard abs. Whoa.

Catelynn Lowell's honey took to Instagram this morning to take a studly selfie, and let's just say that I'm sure she's proud of Tyler's hard work. Check it out ...

Ha, at least he knows he's being a showoff! But he's clearly put in the time and effort required to earn the right to brag a bit! Love seeing that Tyler's so committed to a healthy lifestyle. And I'm sure his dedication is good news for Catelynn, too -- for more than one reason!